The use of mobile communications devices has become commonplace in today's society. As consumers of mobile communications services become more sophisticated, it becomes more important for service providers to offer more and better services in order to fully meet their subscribers' needs. Such value-added services have become an integral part of the consumer's expectations regarding their mobile communications service.
Many of these value-added services relate to the provision of Intelligent Network (IN) services such as video or music download services, automated call forwarding services, ring-back tone services, prepaid services and the like. In the Global System for Mobile Communications (GSM), the Customized Application of Mobile Enhanced Logic (CAMEL) standard has been developed to aid GSM operators to offer operator-specific services to their subscribers, even if a subscriber is roaming outside their home network. These services can include call processing functions such as caller ID and call screening, call forwarding, call rerouting; charging functions such as location-based charging or personal discounts; and provision of tones and announcements to provide information regarding a call to a subscriber's mobile telephone. CAMEL protocol is defined in a set of standards established by the ETSI (European Telecommunication Standardization Institute) and later upgraded as part of 3GPP (Third Generation Partnership Project) initiative. These standards can be found at http://webapp.etsi.org/key/queryform.asp.
Information regarding CAMEL networks can be found in many publications. The most comprehensive work on CAMEL including the latest standardization enhancements can be found in the book entitled, CAMEL, Intelligent Network for the GSM, GPRS and UMTS Networks by Rogier Noldus, published by John, Wiley & Sons Limited (2006). Other publications that describe the architecture and operation of a mobile network using CAMEL functionality include the publication by Paulius Meskauskas entitled “Customised Applications for Mobile Enhanced Logic (CAMEL),” for the Research Seminar on Nomadic Computing for the Department of Computer Science at the University of Helsinki; the CAMEL tutorial by Zahid Ghadialy entitled “CAMEL: An Introduction,” (Jul. 25, 2004), available on the World Wide Web at http://www.3g4g.co.uk/Tutorial/ZG/zg_camel.html; and “An Introduction to GSM Enhancements for Operator Specific Services (CAMEL)” (1996) by David G. Smith, published by the IEEE, Savoy Place, London. Information regarding CAMEL triggers and trigger detection points may also be found in U.S. patent documents such as, for example, U.S. Pat. No. 7,050,811 to Grech et al. and U.S. Patent Application Publication No. 2003/0095566 to Bunting et al.
Information regarding CAMEL networks may also be found in U.S. patent application Ser. No. 11/754,808, entitled “Optimized Camel Triggering for Prepaid Calling,” filed May 29, 2007 by the same inventor hereof, which is hereby expressly incorporated by reference herein in its entirety.
In accordance with the basic structure for a CAMEL network, information about a mobile subscriber is contained in a database in the subscriber's Home Location Register (HLR). This information includes the identity of the mobile station, subscriber information including a subscriber profile, presence information, call forwarding options, subscription to enhanced services such as packet data and the like. The HLR may also maintain CAMEL Subscription Information (CSI) for a mobile subscriber in a CAMEL network, and such a subscriber having CSI will be referred to herein as a “CAMEL subscriber.” When a CAMEL subscriber performs a location update to a different MSC in a GSM network, her subscription information is transferred and maintained in the Visitor Location Register (VLR) for that MSC. In a GSM network, the VLR is a logical entity which is often co-located with the Mobile Switching Center (MSC). When a mobile subscriber having CAMEL services in her home network roams to another network, the CAMEL Subscription Information about that roaming subscriber is temporarily stored in the VLR for that network so that the enhanced services that the subscriber has in her home network are also available to her as she roams. This helps to make a consumer's mobile service truly mobile, since she will experience the same level of service as a “visitor” in another network as she does in her own home network.
CAMEL works to enable the provision of such “seamless” mobile service by providing a protocol, known as the CAMEL Application Part (CAP) for communication between a Mobile Switching Center (MSC) and a Service Control Point (SCP) handling a mobile call, where the SCP is most often a part of the subscriber's home network. CAMEL also provides a Basic Call State Model (BCSM), which describes the different phases of call processing in the MSC. An Originating Basic Call State Model (O-BCSM) describes the call processing for a mobile-originated (MO) call, i.e., a call where the calling party is originating a call from her mobile device, whether the called device is a mobile or non-mobile device. Similarly, a Terminating Basic Call State Model (T-BCSM) describes the call processing to route a terminating call when the mobile device is the recipient of an incoming call.
Both the O-BCSM and T-BCSM contain various points, or states, in the call processing between the MSC and the SCP. Each state is preceded by a transition step, or Detection Point (DP) where the call is handed over to the SCP for a determination whether the call can proceed to the next state. A DP in a CAMEL call can either be an Event Detection Point (EDP) or a Trigger Detection Point (TDP). An EDP is imposed by the SCP during processing of the call, and detects significant events during the call, such as an answer from the called party or disconnection by the calling or called party. A TDP is a part of the processing for all CAMEL calls by a subscriber in a network, and forms a part of a subscriber's CAMEL Subscription Information in the HLR. Both an EDP and TDP can be described as being “armed” if they have been activated and are available for use in processing the call.
One of the services provided in a CAMEL network is prepaid mobile service, both for mobile originators and mobile recipients of calls in the mobile system. Prepaid mobile service is a popular option for many users. It can enable a user to enjoy the benefits of mobile communications without having to enter into a long-term contract. It also can be useful to facilitate management of mobile service, for example, as a parental control tool to manage a child's use of mobile services or as a management tool for corporate usage.
Control of a prepaid or other call in a CAMEL network can be managed by the SCP and the MSC through the use of messages passed between the SCP and the MSC by means of CAP operations. Charging for a prepaid call in a CAMEL network is handled by the SCP based in part on messages from the MSC. CAMEL also provides for processing of a call if the messaging between the MSC and the SCP fails. Failure of the CAP messaging, also known as CAP Dialogue, can result from the loss of signaling path between the MSC and SCP or due to maintenance activity or other error in the SCP. Processing of the call when the CAP messaging fails is decided by a parameter known in the art as “default call handling” that is part of the subscriber's CSI. The default call handling parameter can have one of two values—Release or Continue. If the parameter is set to “Release,” the call will be terminated if the CAP messaging between MSC and SCP fails. If the default call handling parameter is set to “Continue,” the call will be allowed to continue.